<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
    <style>
        img { 
            width: 300px;
        }
    </style>
<body>
    <div></div>
   <button id="ldh">刘德华</button>
   <button id="zxy">张学友</button><br>
   <img src="../p1378956633.91.jpg" alt="" title="刘德华">
    <script>
     //修改元素属性 src
     //1.获取元素
     var ldh = document.getElementById('ldh');
     var zxy = document.getElementById('zxy');
     var img = document.querySelector('img');
     //2.注册事件 
     zxy.onclick = function() {
         img.src = '../p33190.jpg';
         img.title = '张学友'
     }
     ldh.onclick = function() {
         img.src = '../p1378956633.91.jpg';
         img.title = '刘德华'
     }
    </script>
</body>
</html>